The technical principles of the Android support library printing framework III: Printing process analysis

The technical principles of Android support library printing framework III: Printing process analysis The Android support library provides a powerful printing framework that enables developers to implement the printing function in the application.In this article, we will analyze the printing process of the Android support library printing framework to understand its technical principles. In the Android support library printing framework, the printing process is mainly divided into the following steps: 1. Create Printadapter: Developers need to create a printed adapter to implement the Printadapter interface.The adapter is responsible for providing print content and printed configuration parameters, and returns a print document when printing requests. The following is the code of the printed adapter class of an example: public class MyPrintAdapter extends PrintDocumentAdapter { @Override public void onLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras) { // Set the layout of the print document, including page size, border distance, etc. // Layout according to the print content } @Override public void onWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback) { // Write the print content into the file // Depending on the printing needs, the content is written into the file stream } } 2. Register Printadapter: In an application, obtain the print manager object through the Printmanager system, and register the printed adapter into the print manager. The following is the code for the registration of a compatible with an example: PrintManager printManager = (PrintManager) getSystemService(Context.PRINT_SERVICE); String jobName = getString(R.string.app_name) + " Document"; printManager.print(jobName, new MyPrintAdapter(), null); 3. Layout printing document: When the print request enters the system, the system will call the onlyout () method of Printadapter to lay out the printing document.In this method, we can set the layout of the print document, including page size, border distance, etc. 4. Write the print content: When the layout of the print document is determined, the system will call the onwrite () method of Printadapter to generate the print content.In this method, we can write the printing content into the file flow according to the printing needs. 5. Printing output: After the printing content is written, the system will pass the print document to the corresponding printing service for printing output. In general, the printing process of the Android support library printing framework includes the creation of a printing adapter, a registration printing device, a layout printing document, a printing content, and printing output.By understanding the technical principles of the printing process, developers can better use the Android support library to achieve their own printing functions. It is hoped that this article can help readers understand the technical principles and printing processes of the printing framework of the Android support library.If you have any questions, please leave a message.